BACE1 Inhibitor, Neuroprotective, and Neuritogenic Activities of Melatonin Derivatives

Round 1

Reviewer 1 Report

This research article "BACE1 Inhibitor, Neuroprotective and Neuritogenic Activities of Melatonin Derivatives" is an interesting article that brings extra insight into the multiplicity of actions of melatonin against neurodegeneration. However, I have any questions that need to be clarified and included.

1. The authors use a transformed P19-derived neuron to study the neuroprotection and neuritogenesis induced by the compounds. The major problem with this study is the use of P19-derived neuron as a model for neurons. These cells are transformed and immortal from aberrant intracellular signaling, which will have profound effects on the analysis. These cells can become neuron-like with exposure to retinoic acid but use primary neurons have supplanted these tumor cell lines.
2. The investigation carried out by the authors have shown that the active compounds (1, 3 and 5) exhibited activities comparable to that of melatonin. Hence, what would be the advantage(s) to use the compounds developed by the authors instead of melatonin? Can the authors comment on this?
3. Figure 3. Why is the error bar in the melatonin experiment (without FBS) so large? Furthermore, in the 5-MT and compound 3 error bars are also large. It could significantly interfere with the final results.
4. Please provide recommendation for future studies in the discussion section.
5. Please add more critical evaluation of the literature, and an impartial opinion of the pros and cons of melatonin derivatives as neuroprotective agents. In this context, authors should include the next reference: Ramos et al. (2017) Melatonin as a versatile molecule to design novel multitarget hybrids against neurodegeneration. Future Med Chem. 2017 9(8):765-780.

Typos:

Page 2, line 57: Kainate instead of kainite

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Melatonin (MLT) has been reported to be neuroprotective agent and its modified structures exhibited potent antioxidant and anti-inflammation activities. Therefore, the activity against Alzheimer’s disease (AD) of MLT and its derivatives were investigated. Here, the inhibitory activity of MLT derivatives on BACE1 and acetylcholinesterase as well as the neuroprotective and neurogenesis effects on P19-derived neurons were evaluated. 

The experiments are not well designed to support the conclusions and the manuscript is not structured and written properly.

Major Compulsory Revisions

1. Previous study reported that MLT is active on modulating choline acetyltransferase activity but not AChE activity. Therefore, choline acetyltransferase activity but not AChE activity should be investigated in this study.
2. There is no data indicates the statement: “FBS was withdrawn from neuron cells, then, the oxidative stress was generated”. If this is true, then the oxidative stress should be determined.
3. The increase of cell viability after the treatment of MLT derivative may be due to the increase of cell number but not of cell viability. Another assay for cell viability should be performed. Choosing only a low concentration (1 nM) to determine the neuroprotective effect of MLT derivatives cannot correctly indicate its activity, and the neuroprotective effect of higher concentrations of MLT derivatives should also be analyzed. The statistical analysis of Figure 3 should be recalculated. What is “ND’ mean in Figure 3.
4. For neuritogenic study, the morphology of neurites should be shown to elucidate the changes of number, length, and branches of neurite after the treatment of MLT derivatives.
5. The legend is too short to clearly explain its meaning. The text in Figure 2 is blurred and difficult to read.

Minor Essential Revisions

1. Line 57: “kainite” should be “kainate”.
2. Line 92: “experiments which each of them was run in triplicate” should be “experiments, and each of them was run in triplicate”.
3. Line 107: “RMSD” should be “root-mean square error (RMSD)”.
4. Line 108: “GA” should be “genetic algorithm (GA)”.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have addressed all my concerns 

Author Response

We would like to thank you very much for your kind suggestion.

Reviewer 2 Report

The revision of this manuscript is well done. There is only a minor point to be corrected.

Line 183: “prepresented H-bond” should be “represented H-bond”.

Author Response

Thank you for your kind suggestion. We would like to apologize for our mistake. We already corrected the error (page 6, line 183) in the revised version.